Unfortunately, it's confusing too....for example the rule-of-thumb that a 1:72 twist rate won't stabilize a conical at all or well....there are excellent shooting Enfield rifles that are 1:74, and they shoot minnieballs.
The other side of the coin is folks say sometimes that 1:48 is a compromise twist rate to shoot both conical and round ball, not knowing that 1:48 was very popular in rifles before conicals appeared on the scene.
Then there are those who say a faster twist than 1:48 is only for conicals, while Pedersoli sells a Jaeger rifle in 1:24 and recommends patched round ball for that rifle.
As mentioned, though I think you have a good staffer at that gunshop, for I noticed something about your original post. You are in Pennsylvania, so your shop person knows the PA black powder regulations. In PA they have a black powder season where you have to use a patched round ball and a flinter. So the shop person was probably guiding you to what you locally must use, and you might as well learn to shoot that well.
As for me, I prefer the PRB for accuracy AND it kicks a whole lot less. :shocked2: I've gone to the range recently, and "the boys" were tuning up their muzzleloaders that we don't discuss, with 120 - 150 grain loads, and 300 plus grain projectiles...and some of them couldn't really raise their arm to wave goodbye at the end of the day...
LD